Overview of strategies for addressing BRIs in drug discovery: Impact on optimization and design.

The sensitive and specific detection of adducts derived from reactive intermediates during discovery metabolite profiling has been made feasible by advances in LC-MS/MS instrumentation. Many companies employ screens with nucleophilic trapping agents as a routine part of early screening efforts. Although certainly not as straightforward as initial adduct detection, the positives in the profiling experiment can be followed-up with determination of exact adduct structure. This information feeds naturally into drug design efforts as the structural motifs responsible for reactive metabolite formation can be altered to reduce the property. While the process of generation of reactive metabolite data has become more straightforward, the conversion of that data into an optimization paradigm remains challenging. Recent studies have shown a very loose correlation between extent of reactive metabolite formation and observed toxicity, so setting stringent criteria likely leads to discarding compounds that would not have problems. On the other hand, the central role of reactive metabolites in most accepted mechanisms of drug-induced toxicity points to the fact that there is value in minimizing the property. Decision making based on information on reactive metabolite formation remains a difficult process in all phases of drug discovery and development. Decisions on compounds in discovery can be made based on a fixed threshold value or relative to a reference point within a chemical series, but should be made with a firm understanding of the limitation of the data.